Arrays are often used, for example, to determine the amount of various analytes contained within a target solution or sample solution. Briefly, an array may be embodied on a substrate that includes a plurality (typically thousands) of regions or features bearing particular chemical moities. Each region bearing a particular chemical moiety may be referred to as a feature, consisting of a quantity of “probes.” The chemical composition of each probe is chosen so as to indicate the amount of a given analyte within the target solution. The target solution is permitted to commingle with the array, and thereby to commingle with the various probes thereon. Upon commingling, a probe and its corresponding analyte (if present) bind, and this binding interaction is detected, typically through the use of a label (e.g., a fluorescent label) associated with the analyte molecules. The strength of the signal from a given feature indicates the amount of a corresponding analyte contained within the solution.
The aforementioned scheme is predicated upon the notion that a sufficient amount of the target solution reaches each probe on the array, so that the aforementioned reaction may occur in the time allotted. In some instances, the amount of target material (i.e., the material dissolved to create the solution carrying the various analytes) is limited. For example, in circumstances in which DNA or RNA is used as the target material, its availability is oftentimes limited. Amplification techniques may be used to increase the amount of analyte. However, it may be advantageous to perform the aforementioned hybridization operation without resort to amplification techniques to generate additional target material. It is the general property of array hybridization kinetics that for a given amount of target the hybridization rate will be dependent on target concentration among other things. For example, one may dissolve the relatively small amount of target material in a relatively large volume of solvent, but due to the resulting low concentration of target material, such an approach may lead to a lengthy hybridization time (e.g., 40 hours). On the other hand one may dissolve the relatively small amount of target material in a relatively small volume of solvent resulting in a shorter hybridization time. To ensure that a sufficient amount of the target solution reaches each probe on the array, mixing is often advantageous. It can be difficult to efficiently mix small volumes of target solution on an array surface. Existing mixing techniques, especially for small volumes, require the use of costly specialized equipment. Techniques that do not rely on mixing, such as array hybridization under a statically positioned coverslip, allow for the use of small volumes of solvent, but the beneficial effects of mixing are not present.
As suggested by the foregoing, there exists an opportunity for an improved hybridization technique for use with low volumes of target solution. Such a technique may efficiently hybridize a small quantity of target material held in a small volume of solvent in a relatively short amount of time. Further, such a technique may be carried out using equipment also suitable for larger volume hybridzations.